Cook the rice with the water according to package instructions. Fluff and set aside.

In a small bowl, mix all of the spices together. Season the steak with salt and pepper, then rub just half of the spice mixture evenly over the steak.

Heat just half of the oil in a skillet over medium heat. Add the steak and cook for about 4 minutes per side, or until it reaches your desired doneness (medium-rare is about 135°F / 57°C). Transfer the steak to a plate and let it rest for 5-10 minutes, then dice into cubes.

In the same skillet, heat the remaining oil over medium heat. Add the corn and cook for 4-5 minutes, until heated through and starting to char. Stir in the remaining spice mix and cook for 1 minute longer. (If you prefer warm beans, add the black beans to the skillet with the corn and cook for 2-3 minutes, until heated through.) Remove from heat.

To assemble, divide the rice among bowls and top with the diced steak, corn, guacamole, black beans, lettuce, and cheese. Serve as is, or add salsa, hot sauce, or any other low-calorie condiments you like.